The present invention relates to systems and methods for the miniaturization of read/write heads. More particularly, the present invention relates to systems and methods for miniaturizing tape heads using micro-electromechanical systems (MEMS). Particular utility for the present invention is in the design and method of use of tape heads, although other utilities are contemplated herein, for example, hard disk drive heads and floppy disk drive heads, and/or other read/write media using read/write heads.
Current tape head technology has considerably changed from the early wire-wound read-write elements. Today""s magnetic tape heads have thin-film write elements and magneto-resistive read elements. Future tape heads may replace the magneto-resistive read elements with giant magneto-resistive, sometimes called spin-valve, read elements. Far into the future, tape heads may have tunnel junction read elements for reading magnetic tape or may even have laser read and write elements for performing I/O on optical tape.
Regardless of the technology to read and write data, tape heads are typically built to provide read-after-write. Read-after-write means that the data is read-verified after it is written, to check for write errors. Since write errors are the most difficult to correct, immediately checking for write errors via a read-verification enhances the reliability of the tape drive. This read-after-write is provided by a tape head by having each read element (a) be in-line, rather than side-by-side, with the respective write element and (b) the read element be behind the respective write element according to the direction that the tape is moving across the tape head.
Up until now, tape heads have typically been built using read and write elements photolithographed onto ferrite modules and these modules fixedly assembled into the tape head. No motion of the read and write elements within the tape head was permitted. Air bleed slots were typically formed in the outer surface of the ferrite modules, so that the boundary layer of air between the moving tape and the read and write elements could be bled off. Bleeding off this boundary layer of air is critical to keeping the tape in close proximity with the read and write elements on the tape head.
In the IBM 3420 and 3480 tape drives, the assembled tape head was aligned with respect to tape guides and fixedly held in place in the tape drive. Since the tape head was fixedly held in place, the IBM 3420 and 3480 magnetic tape did not have servo tracks. Eventually this static positioning of the tape head gave way to articulated tape heads, such as used in the IBM 3590 tape drive and taught in U.S. Pat. No. 5,377,052; which is hereby incorporated by reference. Via a parallelogram support, the tape head in the IBM 3590 tape drive was moved perpendicular to the direction of travel of the magnetic tape. The magnetic tape used in the IBM 3590 tape drive now had longitudinal servo tracks, as taught in U.S. Pat. No. 5,432,652; which is also hereby incorporated by reference. Using servo read elements on the tape head, the tape drive read the position of the tape head relative to the factory written servo tracks and adjusted the position of the tape head to optimize I/O.
The tape heads used in the IBM 3420, 3480, and 3590 tended to be somewhat large in size. Later tape drives, such as IBM""s Linear Tape Open, used a lead screw as a coarse actuator and a magnetically activated flexible beam as a fine actuator. Both the coarse and the fine actuators move the now much smaller tape head perpendicular to the direction that the tape was moving. The coarse actuator moved the tape head large distances so that the head could access all recording regions on the tape. The fine actuator, which rode on top of the coarse actuator, moved the tape head small but accurately controlled distances, so that the head could dynamically follow the motion of the tape. Improvements to the servo tracks written to the magnetic tape used in the Linear Tape Open drive, IBM""s Timing Based Servo, are taught in U.S. Pat. No. 5,689,384, which is hereby incorporated by reference. These improvements to tape drives, tape heads, and tape itself greatly increased the data capacity and reliability of tape data storage.
Improvement in tape technology was needed to obtain yet further gains in data capacity and reliability. Further reduction of the mass of the tape head was needed in order to enhance the dynamic responsiveness of the fine actuator mechanism so that the tape head can better track the motion of the moving tape, thus improving the data capacity and reliability of the tape drive. This need for improvement has culminated with MEMS technology to move the I/O elements themselves as a fine actuator mechanism. The read and write elements are now placed on microsliders, which are dynamically moved perpendicular to the motion of the tape by micromotors. The motion of the microsliders is constrained by walls in the ferrite core or head block.
Servo read elements on the microsliders feed positional information to the tape drive. The tape drive continually looks at the error term between the actual position and the desired position of the microsliders, based on the reading of servo tracks which have been factory written on the tape itself. The tape drive then activates micromotors to move the microsliders in order that the data read and write elements follow the lateral motion of the tape. Thus, the data read and write elements remain centered over the desired data tracks as I/O is performed between the tape drive and the tape. The coarse actuator, intended to move the tape head to new areas of the tape, continues to move the entire tape head as needed.
In one exemplary embodiment, the present invention provides a tape head that includes a body portion comprising a cavity, a microslider movably disposed in the cavity comprising at least one read element disposed thereon, and a controllable micromotor coupled to the microslider for moving the microslider in the cavity.
Other exemplary embodiments include a control system for actuating the micromotor to cause the microslider to move with respect to the body cavity.
It will be appreciated by those skilled in the art that although the following Detailed Description will proceed with reference being made to preferred embodiments and methods of use, the present invention is not intended to be limited to these preferred embodiments and methods of use. Rather, the present invention is of broad scope and is intended to be limited as only set forth in the accompanying claims.
Other features and advantages of the present invention will become apparent as the following Detailed Description proceeds, and upon reference to the Drawings, wherein like numerals depict like parts, and wherein: